PlantUML (https://plantuml.com/) is used to generate the diagrams.
The JAR file and simple generate script are included.
../generate.sh [options...] file.puml
Create PNG image:
../generate.sh hrStaff-proposed.puml && start hrStaff-proposed.png
Create a URL encoding of the diagram:
../generate.sh -encodeurl file.puml
The encoded diagram can be embedded to a web page using an image tag:
<img source="http://scs-dockerl1.scview.int:8888/svg/encoded_image"/>
Or in YouTrack Markdown:

The value of "encoded_image" is determiend by using the -encodeurl option above.
http://scs-dockerl1.scview.int:8888 is an internal PlantUML server running at SCSS. Any
public PlantUML server will do.